Fixation device that heats a fixation belt by an electromagnetic induction heating method

Abstract

According to an embodiment, a fixation device has a fixation belt, a coil, and a heat-generation auxiliary plate. The coil is opposed to the fixation belt and the heat-generation auxiliary plate and generates magnetic flux. The heat-generation auxiliary plate assists heating of a recording medium by the fixation belt. The heat-generation auxiliary plate has a magnetic layer and a non-magnetic layer formed on the magnetic layer and contacting a base layer of the fixation belt. The non-magnetic layer is harder than the base layer of the fixation belt.

What is claimed is: 
     
       1. A fixation device that fixes a toner image formed on a recording medium onto the recording medium, the fixation device comprising:
 a fixation belt having a base layer and an electrically-conductive layer formed on the base layer and configured to heat the toner image by generating heat by the electrically-conductive layer in order to fix the toner image onto the recording medium; 
 a coil opposed to the fixation belt and configured to cause the electrically-conductive layer to generate heat by generating magnetic flux; and 
 a heat-generation auxiliary plate having a magnetic layer and a non-magnetic layer and configured to assist the heating of the recording medium by the fixation belt, the magnetic layer containing a magnetic material and opposed to the coil with the fixation belt interposed therebetween, the non-magnetic layer formed on the magnetic layer, containing a non-magnetic material harder than the base layer of the fixation belt, and contacting the base layer of the fixation belt, wherein 
 the non-magnetic layer of the heat-generation auxiliary plate has a thickness of 1 μm or less. 
 
     
     
       2. The fixation device according to  claim 1 , wherein
 the fixation belt is a tubular endless belt, and 
 the heat-generation auxiliary plate is disposed on an inner peripheral side of the fixation belt. 
 
     
     
       3. The fixation device according to  claim 1 , wherein
 the fixation belt has a protective layer formed on the base layer with the electrically-conductive layer interposed therebetween. 
 
     
     
       4. The fixation device according to  claim 1 , wherein
 the electrically-conductive layer of the fixation belt is a thin layer having a small heat capacity. 
 
     
     
       5. The fixation device according to  claim 1 , wherein
 the heat-generation auxiliary plate is disposed on the fixation belt in a pressed state. 
 
     
     
       6. The fixation device according to  claim 1 , wherein
 the magnetic layer of the heat-generation auxiliary plate is a thin metal member made of a magnetic shunt alloy having a Curie point of 220° C. to 230° C. 
 
     
     
       7. The fixation device according to  claim 1 , wherein
 the coil causes the magnetic layer to generate heat by generating the magnetic flux, and 
 the heat-generation auxiliary plate assists the heating of the recording medium by the fixation belt through the heat generation of the electrically-conductive layer. 
 
     
     
       8. The fixation device according to  claim 1 , wherein
 the non-magnetic layer of the heat-generation auxiliary plate is formed by plating on the magnetic layer. 
 
     
     
       9. The fixation device according to  claim 1 , wherein
 the non-magnetic layer of the heat-generation auxiliary plate contains tin or a tin alloy. 
 
     
     
       10. The fixation device according to  claim 1 , wherein
 the fixation belt and the non-magnetic layer of the heat-generation auxiliary plate contact each other via lubricant oil. 
 
     
     
       11. The fixation device according to  claim 1 , wherein,
 between the magnetic layer and the non-magnetic layer, the heat-generation auxiliary plate has a binder layer having the same thickness as the non-magnetic layer or a thickness smaller than that of the non-magnetic layer. 
 
     
     
       12. An image formation apparatus comprising:
 a supply unit configured to supply a recording medium on which a toner image is formed; 
 an image formation unit configured to form a toner image on an image carrier; 
 a transfer unit configured to transfer the toner image formed on the image carrier onto the recording medium; and 
 a fixation device configured to fix the transferred toner image onto the supplied recording medium, wherein 
 the fixation device further has:
 a fixation belt having a base layer and an electrically-conductive layer formed above the base layer and configured to heat the toner image by generating heat by the electrically-conductive layer in order to fix the toner image onto the recording medium; 
 a coil opposed to the fixation belt and configured to cause the electrically-conductive layer to generate heat by generating magnetic flux; and 
 a heat-generation auxiliary plate having a magnetic layer and a non-magnetic layer and configured to assist the heating of the recording medium by the fixation belt, the magnetic layer containing a magnetic material and opposed to the coil with the fixation belt interposed therebetween, the non-magnetic layer formed on the magnetic layer, containing a non-magnetic material harder than the base layer of the fixation belt, and contacting the base layer of the fixation belt, and 
 
 the non-magnetic layer of the heat-generation auxiliary plate has a thickness of 1 μm or less. 
 
     
     
       13. The image formation apparatus according to  claim 12 , wherein
 the non-magnetic layer of the heat-generation auxiliary plate is formed by plating on the magnetic layer. 
 
     
     
       14. The image formation apparatus according to  claim 12 , wherein
 the non-magnetic layer of the heat-generation auxiliary plate contains tin or a tin alloy. 
 
     
     
       15. The image formation apparatus according to  claim 12 , wherein
 the fixation belt and the non-magnetic layer of the heat-generation auxiliary plate contact each other via lubricant oil. 
 
     
     
       16. An image formation apparatus comprising:
 a supply unit configured to supply a recording medium on which a toner image is formed; 
 an image formation unit configured to form a toner image on an image carrier; 
 a transfer unit configured to transfer the toner image formed on the image carrier onto the recording medium; and 
 a fixation device configured to fix the transferred toner image onto the supplied recording medium, wherein 
 the fixation device further has:
 a fixation belt having a base layer and an electrically-conductive layer formed above the base layer and configured to heat the toner image by generating heat by the electrically-conductive layer in order to fix the toner image onto the recording medium; 
 a coil opposed to the fixation belt and configured to cause the electrically-conductive layer to generate heat by generating magnetic flux; and 
 a heat-generation auxiliary plate having a magnetic layer and a non-magnetic layer and configured to assist the heating of the recording medium by the fixation belt, the magnetic layer containing a magnetic material and opposed to the coil with the fixation belt interposed therebetween, the non-magnetic layer formed on the magnetic layer, containing a non-magnetic material harder than the base layer of the fixation belt, and contacting the base layer of the fixation belt, wherein 
 
 between the magnetic layer and the non-magnetic layer, the heat-generation auxiliary plate has a binder layer having the same thickness as the non-magnetic layer or a thickness smaller than that of the non-magnetic layer. 
 
     
     
       17. The image forming apparatus according to  claim 16 , wherein the non-magnetic layer of the heat-generation auxiliary plate is formed by plating on the magnetic layer. 
     
     
       18. The image forming apparatus according to  claim 16 , wherein the non-magnetic layer of the heat-generation auxiliary plate contains tin or a tin alloy. 
     
     
       19. The image forming apparatus according to  claim 16 , wherein the fixation belt and the non-magnetic layer of the heat-generation auxiliary plate contact each other via lubricant oil.